WASHINGTON - A conservative group is threatening to sue the Secret Service for religious discrimination over security guidelines that would ban Christian crosses from President Bush's inaugural parade route.

The Secret Service said Monday the guidelines were meant to prohibit large structures that could be used as weapons. Crosses were the only religious symbols on the list of banned items.

In a Dec. 17 directive to the National Park Service, the Secret Service mandated that signs and placards along the inaugural parade route down Pennsylvania Avenue be made out of cardboard, poster board or cloth. They may be no more than 3 feet wide or 20 feet long.